Method for treating reinforcing fibre and method for producing a reinforced composite article from the treated fibre

ABSTRACT

The present invention relates to a reinforced composite material and a method for its production. The composite material comprises at least one cured resin having a reinforcing material. Preferably the reinforcing material is a plurality of glass fibres which are treated such that the properties of the interphase substantially surrounding each fibre are substantially equivalent to those of the bulk cured resin. The fibre treatment may be selected from the group consisting of a polymeric coating, a hydrophilic surface coating, a surface coating of a free radical inhibitor, or a reduction in the total surface area of the fibres. The reinforced composite material of the invention provides improved long-term mechanical properties compared to traditional glass fibre reinforced materials.

FIELD OF THE INVENTION

The present invention relates to reinforced composite materials, and inparticular to fibre reinforced polymer composites. However, it will beappreciated that the invention is not limited to this particular fieldof use.

BACKGROUND OF THE INVENTION

Any discussion of the prior art throughout the specification should inno way be considered as an admission that such prior art is widely knownor forms part of the common general knowledge in the field.

Fibre reinforced polymer composites are known in the art and arecommonly made by reacting a curable resin with a reactive diluent in thepresence of a free radical initiator. Typically, the curable resin is anunsaturated polyester resin and the reactive diluent is a vinyl monomer.Reinforcing materials such as glass fibre are often included in theformulations to provide dimensional stability and toughness. Suchreinforced composites are used in many key industrial applications,including: construction, automotive, aerospace, marine and for corrosionresistant products.

For traditional glass fibre reinforced polymer composites, the fibrelengths typically range from about 12 mm up to tens of meters in thecase of, for example, filament winding. In these glass fibre polymercomposites the majority of fibres are held in position by mechanicalfriction and there is only relatively weak bonding of the fibres to theresin matrix. Therefore, the performance of such polymer composites islargely due to the length of the fibres employed and in these compositesthere is a discontinuity/gap between the fibres and the resin. Cracksinitiated in the resin matrix find it very difficult to jump gaps,therefore in these composites cracks initiated in the resin are usuallyarrested at the resin boundary and do not reach the glass surface.However, traditional glass fibre composites have a number ofshortcomings. For example, it is difficult to “wet” the fibres with theresin prior to curing, and even dispersion of long fibres throughout thecomposite is difficult, especially for complex parts.

In addition, such traditional glass reinforced polymer composites arelimited by their production techniques which generally require manuallayering or are extremely limited in the shape and complexity of themoulds.

To overcome these shortcomings, very short glass fibres may be used.VSFPLCs or very short fibre polymerisable liquid composites can productlaminate with tensile strengths greater than 80 MPa flexural strengthgreater than 130 MPa. VSFPLCs are suspension of very short surfacetreated reinforcing fibres and polymerisable resins/thermoset such as UPresins vinyl functional resins, epoxy resins or polyurethane resins. Thelength of the fibres are kept very short so that they do not increasethe viscosity of the liquid to where the resin fibre mixture is nolonger sprayable or pumpable. VSFPLCs can be used to replace standardfibre glass layouts in open and closed moulding applications and alsocan be used as alternatives to thermoplastics in resin injectionmoulding and rotation moulding applications.

However, an improvement in the fibre-to-matrix bond is typicallyrequired since such very short glass fibres are too short to bemechanically “keyed” into the matrix. Coating the reinforcing fibre witha coupling agent may provide an improvement in the fibre-to-matrix bond.For example, one commonly used coupling agent is Dow Corning Z-6030,which is a bifunctional silane containing a methacrylate reactiveorganic group and 3 methoxysilyl groups. Dow Corning Z-6030 reacts withorganic thermoset resins as well as inorganic minerals such as the glassfibre. Whilst such coupling agents may improve the fibre-to-matrix bond,the usefulness of the reinforced polymer composite is limited since theyare prone to embrittlement over time. A product with greater flexibilityand toughness is sometimes needed.

An attempt was made to address some of these shortcomings in PCT PatentApplication No. PCT/AU01/01484 (International Publication No. WO02/40577) where the coupling agent was pre-polymerised prior to coatingthe glass reinforcing fibre to “plasticise the interface”. The intentionof the pre-polymerised coupling agent was to provide a rubberyinterphase between the fibre and the bulk resin and thereby result inproduct having improved impact resistance and strength. However,long-term embrittlement is still an issue with the above PCT. In VeryShort Fibre Polymerisable Liquid Composites there are no air gapsbetween the fibre and the resin. In VSFPLCs the resin is chemicallybonded to the resin matrix and there are no gaps between the resin andthe fibres. Cracks initiated in the resin matrix travel directly to thefibre surface. All the energy of the propagating crack is focused at apoint on the glass fibre, and the energy is sufficient to rupture thefibre. Abundant evidence for this can be seen on the fracture surface ofsilane treated fibres. This is especially true for laminates withflexural strengths greater than 100 MPa.

It is an object of the present invention to overcome or ameliorate atleast one of the disadvantages of the abovementioned prior art, or toprovide a useful alternative.

DISCLOSURE OF THE INVENTION

According to a first aspect the present invention provides a method forproducing a reinforced composite material, comprising: combining atleast one curable resin and a plurality of reinforcing fibres; andcuring the at least one curable resin, the cured resin adjacent thereinforcing fibres defining an interphase, wherein the reinforcingfibres are treated such that the properties of the interphase aresubstantially equivalent to those of the bulk cured resin.

In a preferred embodiment the reinforcing fibres are glass fibres havinga coupling agent coupled thereto. The glass fibres may be chosen fromE-, S- or C-class glass. The glass fibre length is typically betweenabout 100 and 1000 microns and the fibres are preferably evenlydispersed through the resin. The coupling agent comprises a plurality ofmolecules, each having a first end adapted to bond to the glass fibreand a second end adapted to bond to the resin when cured. Preferably thecoupling agent is Dow Corning Z-6030. However, other coupling agents maybe used such as Dow Corning Z-6032, and Z-6075. Similar coupling agentsare available from De Gussa and Crompton Specialties.

The properties of the interphase which are substantially equivalent tothose of the bulk resin may be mechanical properties selected from thegroup consisting of strength, toughness, and brittleness. Alternatively,or additionally, the properties may be physical or chemical propertiesselected from the group consisting of density, cross-link density,molecular weight, chemical resistance and degree of crystallinity.

The curable resin(s) preferably includes a polymer and is chosen to havepredetermined properties including from one or more of improved tearresistance, strength, toughness, and resistance to embrittlement.Preferably the resin is chosen such that in its cured state it has aflexural toughness greater than 3 Joules according to a standard flexuretest for a test piece having dimensions about 100 mm length, 15 mm widthand 5 mm depth. Ideally the cured resin having the polymer has aflexural toughness greater than 3 Joules up to 5 years followingproduction.

In preferred embodiments the cured resin is resistant to crackpropagation. A preferred cured resin is able to supply fibrils in enoughquantity and with enough inherent tensile strength to stabilise thecraze zone ahead of the crack, limiting or preventing the propagation ofa crack. Ideally the polymer-modified curable resin arrests the crackbefore it can reach the surface of the glass fibre, or if the crazeahead of the crack reaches the glass it has insufficient energy torupture the glass fibre surface. Such toughened resins are ideallysuited to very short fibre reinforced composites. In addition, suchresins provide reduced embrittlement with age. NOTE: The very surface ofthe glass fibre is nowhere near the strength of the fibre itself due tovastly different cooling rates between the surface of the glass fibreand the body of the glass fibre. This surface is very easily ruptured.To illustrate this one has only to look at the process for making“glue-chipped” decorative glass panels.

The treatment applied to the fibres is preferably a treatment thatreduces catalysation of resin polymerisation in the interphase. In oneembodiment the treatment applied to the reinforcing fibres is theapplication of a polymeric coating. Preferably the polymer of thepolymeric coating is a monomer deficient (less than about 33% w/wmonomer) low activity unsaturated polyester resin having only arelatively moderate amount of unsaturation. Desirably the unsaturatedpolyester resin is formulated to be substantially hydrophilic.

In another embodiment, the treatment applied to the reinforcing fibresis the application of a hydrophilic surface coating. Reacting thecoupling agent (coating the glass fibre) with a hydrophilic agentprovides the hydrophilic surface coating. In a preferred aspect thehydrophilic agent is provided by reacting Dow Corning Z-6030 with atri-hydroxy compound, such as trimetholylpropane, or a tetra-hydroxycompound, such as pentaerythritol in the presence of a catalyst, such astri-butyl tin. The glass reinforcing fibre is sufficiently coated withthe hydrophilic surface coating such that the modified fibre issubstantially hydrophilic.

In a further aspect of the hydrophilic surface coating embodiment, thetreated glass fibre is further treated with an emulsion. The treatmentmay simply be mixing, however compounding is preferred. The emulsionpreferably comprises:

-   -   16.6 parts water;    -   100 parts acetone; and    -   200 parts polymer,        Optionally the emulsion comprises free radical inhibitors, which        generally include hydroquinone (HQ) or hindered amines. The        polymer may be a vinyl ester resin, however the polymers        referred to above are preferred. In particular, the polymer is a        monomer deficient (less than about 33% w/w monomer) low activity        unsaturated polyester resin having only a relatively moderate        amount of unsaturation. Desirably the unsaturated polyester        resin is formulated to be substantially hydrophilic.

In a further embodiment the treatment applied to the reinforcing fibresis the application of a coating of a free radical inhibitor, such ashydroquinone acetyl acetone, hindered phenols or hindered amines. In yeta further embodiment the treatment applied to the reinforcing fibres isthe reduction in the total surface area of the reinforcing fibres.

As discussed above, very short fibre polymerisable liquid compositestypically require the use of coupling agents to improve thefibre-to-matrix bond since the fibres are too short to mechanically keyinto the matrix. The present applicants have found that use of suchcoupling agents tends to cause embrittlement of the reinforced compositematerial over time. Others have attempted to mitigate such embrittlementby using a blend of resins whereby at least one of the resins is“rubbery”. Other alternatives have been to modify the coupling agent toprovide a “rubbery” phase surrounding the fibre, such as disclosed in WO02/40577. The present invention takes an entirely different approach.

Without wishing to be bound by theory, it is believed that prior artcoupling agents coated to the glass fibre act to catalyse resinpolymerisation in the interphase, ie the region directly adjacent theglass fibre, thereby forming a brittle interphase over time. Theapproach of the present invention is to chemically “passivate” thecoupling agent coating, thereby attempting to mitigate any effects whichthe coupling agent may have on the fibre-resin interphase, and enablingthe interphase to have substantially equivalent properties to those ofthe bulk cured resin. However, as the skilled person will appreciate,the degree of passivation should be sufficient to mitigate any effectswhich the coupling agent may have on the fibre-resin interphase whilststill achieving sufficient bonding of the fibre to the bulk resin.

The applicants have found that the present invention, which is entirelycontradictory to the prior art, somewhat surprisingly provides areinforced composite material which exhibits relatively reducedembrittlement as compared to prior art glass reinforced compositematerials whilst retaining properties such as strength, toughness andheat distortion temperature. In particular, the long-term embrittlementissue of prior art composites employing coupled fibres is notablyreduced.

According to a second aspect the present invention provides a reinforcedcomposite material comprising: at least one cured resin having aplurality of reinforcing fibres, the cured resin adjacent thereinforcing fibres defining an interphase, the interphase havingproperties substantially equivalent to those of the bulk cured resin.

According to a third aspect the present invention provides a method fortreating a reinforcing fibre for use in a composite material including acurable resin, the method comprising the step of applying one or more ofa polymeric coating, a hydrophilic surface coating, or a coating of afree radical inhibitor to the reinforcing fibre such that, in use, thecured resin adjacent the reinforcing fibre defines an interphase, theinterphase having properties substantially equivalent to those of thebulk cured resin.

According to a fourth aspect the present invention provides areinforcing fibre for use in a composite material including a curableresin, the reinforcing fibre having one or more of a polymeric coating,a hydrophilic surface coating, or a coating of a free radical inhibitorapplied thereto such that, in use, the cured resin adjacent thereinforcing fibre defines an interphase, the interphase havingproperties substantially equivalent to those of the bulk cured resin.

According to a fifth aspect the present invention provides a method forreducing embrittlement in a composite material having a curable resinand a plurality of reinforcing fibres dispersed therethrough, the curedresin adjacent the reinforcing fibres defining an interphase, the methodcomprising the step of reducing the total surface area of thereinforcing fibres thereby providing a corresponding decrease in thequantity of the interphase.

According to a sixth aspect the present invention provides a mouldedcomposite body according to the first aspect of the invention.

According to a seventh aspect the present invention provides a treatedreinforcing fibre according to the third aspect of the invention.

According to a eighth aspect the present invention provides a method formoulding a composite comprising the steps of providing a mixture of atleast one curable resin and a plurality of reinforcing fibres accordingto the fourth aspect, applying the mixture to a mould and curing the atleast one curable resin.

According to a ninth aspect the present invention provides a mouldedcomposite material when produced by the method according to the eighthaspect.

According to a tenth aspect the present invention provides a liquidcurable composite comprising at least one curable resin and a pluralityof reinforcing fibres such that, in use, the cured resin adjacent saidreinforcing fibres defines an interphase, wherein said reinforcingfibres are treated such that the properties of said interphase aresubstantially equivalent to those of the bulk cured resin.

According to an eleventh aspect the present invention provides a liquidcurable composite comprising at least one curable resin and a pluralityof reinforcing fibres, said reinforcing fibres having one or more of apolymeric coating, a hydrophilic surface coating, or a coating of a freeradical inhibitor applied thereto such that, when cured, the cured resinadjacent said reinforcing fibre defines an interphase, said interphasehaving properties substantially equivalent to those of the bulk curedresin.

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words ‘comprise’, ‘comprising’, and thelike are to be construed in an inclusive sense as opposed to anexclusive or exhaustive sense; that is to say, in the sense of“including, but not limited to”.

Other than in the examples, or where otherwise indicated, all numbersexpressing quantities of ingredients or reaction conditions used hereinare to be understood as modified in all instances by the term “about”.The examples are not intended to limit the scope of the invention. Inwhat follows, or where otherwise indicated, “%” will mean “weight %”,“ratio” will mean “weight ratio” and “parts” will mean “weight parts”.

In describing and claiming the present invention, the followingterminology will be used in accordance with the definitions set outbelow. It is also to be understood that the terminology used herein isfor the purpose of describing particular embodiments of the inventiononly and is not intended to be limiting.

Throughout this specification the terms “fibre” and “fibres” are to betaken to include platelet and platelets respectively. Glass fibres arethe most suitable fibres for the invention. However other mineral fibressuch as wollastonite and ceramic fibres may also be used withoutdeparting from the scope of the invention

Throughout this specification the terms “property” and “properties” areto be taken to include typical mechanical, physical and chemicalproperties of polymers and cured resins. For example, mechanicalproperties are those selected from the group consisting of flexuraland/or tensile strength, toughness, elasticity, plasticity, ductility,brittleness and impact resistance. Chemical and physical properties arethose selected from the group consisting of density, hardness,cross-link density, molecular weight, chemical resistance and degree ofcrystallinity.

Throughout this specification the terms “catalyse” and “catalysation”are to be taken to be synonymous with the terms “initiate” and“initiation” in relation to free radical polymerization.

It will also be understood that the term “material” in the presentapplication refers to liquid and solid forms of the fibre/resin mixture.The material itself can be provided in cured form, uncured liquid formor as a separate component e.g. reinforcing fibres and resin separatelyfor mixing on site.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention provides a method for producing a reinforcedcomposite material and the composite body produced by the method. Themethod comprises the steps of combining at least one curable resin witha plurality of reinforcing fibres such that the fibres are substantiallyevenly dispersed throughout the resin, and curing the resin. Preferablythe resin is a vinyl ester resin having about 40% of a reactive diluent,such as styrene monomer. However, other monomers may also be used, suchas mono- and di- and tri-functional acrylates and methacrylates.Alternatively, the resin may be chosen from unsaturated polyesterresins, epoxy vinyl ester resins, vinyl function resins, tough vinylfunctional urethane resins, tough vinyl functional acrylic resins, andnon-plasticised flexible polyester resins, and combinations thereof.

In preferred embodiments, the fibres are glass fibres chosen from E-, S-and C-class glass having a length of between about 100 and 1000 microns.However, fibres having lengths greater then 1000 microns can also beused. Preferably any sizing agent is removed from the glass fibre priorto its treatment with the coupling agent(s). The preferred couplingagent is Dow Corning Z-6030. However, other coupling agents may be usedsuch as Dow Corning Z-6032 and Z-6075.

The, at least one curable resin may include a polymer, is chosen ormodified with such a polymer to have predetermined properties chosenfrom one or more of improved tear resistance, strength, toughness, andresistance to embrittlement. Preferably the polymer-modified cured resinhas a flexural toughness greater than 3 Joules for up to 5 yearsfollowing production for a test piece having dimensions about 110 mmlength, 15 mm width and 5 mm depth subjected to a standard flexure test.

In preferred embodiments the polymer-modified curable resin is resistantto crack propagation. Such polymer-modified resins provide reducedembrittlement with age. Preferably the polymer is a monomer deficient(less than about 30% w/w monomer) low activity unsaturated polyesterresin having only a relatively moderate amount of unsaturation. Examplesof such polyesters are provided in the tables below. Desirably thesepolyesters are hydrophilic.

Once the resin is cured to provide the reinforced composite material,the cured resin adjacent and substantially surrounding each of the glassreinforcing fibres defines an interphase, and the reinforcing fibres aretreated prior to their addition to the curable resin such that theproperties of the interphase are substantially equivalent to those ofthe bulk cured resin. In one embodiment, the treatment applied to thefibres is a polymeric coating. The polymer of the polymeric coating ispreferably the low activity unsaturated polyester resin described above.

As discussed above, without wishing to be bound by theory the applicantbelieves that a fibre treated with prior art coupling agents acts tocatalyse resin polymerisation thereby forming an interphase havingsubstantially different properties to the bulk cured resin. Aninterphase having highly cross-linked material will have propertiesvastly different to those of the bulk resin, thereby affecting themechanical and physical properties of the final cured reinforcedcomposite body. For example, an interphase having highly cross-linkedmaterial is inherently more brittle than the bulk resin. Duringfracture, a propagating crack will relatively easily rupture thisbrittle interphase and any crack-arresting properties of the resin inthe interphase will substantially reduced. Further, as the skilledperson will appreciate, the more fibre employed in the composite bodythe greater the total amount of brittle interphase will result, and themore brittle the composite body will become.

By treating the coupled glass fibre to reduce catalysation of freeradical polymerisation, the applicants have been able to reduce theeffect of the coupled glass fibre on the interphase such that theinterphase has similar properties to the bulk cured resin. In otherembodiments, the surface of the glass fibre is treated with a coating ofone or more free radical inhibitors, such as hydroquinone or acetylacetone, hindered phenols and hindered amines. The coating of freeradical inhibitor(s) is associated with the surface of the glass fibresuch that catalyzation of resin polymerisation in the interphase isreduced and the interphase has similar properties to the bulk curedresin.

In a further embodiment, the treatment is a reduction in the totalsurface area of the fibres. For example, this may be achieved bysubstituting the glass fibre with a glass fibre having a relativelylarger diameter. To explain, glass fibres typically used in glass fibrereinforced composites have diameters between about 5-12 microns.However, the applicants have discovered that use of glass fibres havingdiameters between about 15-24 microns provides significantly lessembrittlement to the final properties of the reinforced composite body,since for a given weight of glass fibre the total surface area isinversely proportional to the increase in fibre diameter. Of course evenlarger diameter fibres can be used than 24 micron, however, there is apractical working limit of the fibre properties.

In this embodiment, whilst the glass surface still may catalyse resinpolymerisation to produce a brittle interphase, the total amount ofbrittle interphase material is relatively reduced. In addition, toprovide a final cured polymer composite with similar mechanicalproperties, the length of relatively larger diameter glass fibre used ispreferably longer than that which would ordinarily be employed for therelatively smaller diameter fibre.

As the skilled person would be aware, combinations of theabove-described embodiments may also be employed where appropriate. Forexample, it would be possible to use glass fibres having a relativelylarger diameter and coat the fibre with a free radical inhibitor, orcoat the fibre with a polymer as described above.

In further embodiments, the treatment comprises a two-step processwhereby the glass fibre is firstly coated with a first agent and then asecond agent is reacted with the first agent to provide a substantiallyhydrophilic surface-modified glass fibre. Preferably the first agent isa coupling agent having a first end adapted to bond to the fibre, and asecond end adapted to bond either to the second agent or the resin whencured. In a preferred embodiment, the coupling agent ismethacryloxypropyltrimethoxysilane (Dow Corning Z-6030). The secondagent comprises the reaction product between the first agent and atri-hydroxy compound such as trimetholylpropane. However, in alternativeembodiments the hydroxy compound is a tetra-hydroxy compound such aspentaerythritol. The reaction of Z-6030 and trimetholylpropane isconducted in the presence of a tin catalyst, such as tri-butyl tin,under appropriate reaction conditions.

The method of treating the glass fibre according to the previousembodiment further includes the step of mixing or compounding the coatedreinforcing fibre with an emulsion. The emulsion preferably comprises:16.6 parts water, 100 parts acetone and 200 parts polymer, wherein thepolymer is preferably the hydrophilic low activity unsaturated polyesterresin discussed above. The emulsion may also include a hydrophilic freeradical inhibitor such as HQ.

EXAMPLES

The present invention will now be described with reference to thefollowing examples which should be considered in all respects asillustrative and non-restrictive.

Treatment of a Glass Fibre with a Hydrophilic Surface Coating

-   -   1. E-glass fibres were cut to an average fibre length of 3400        micron and then milled to an average length of 700 micron.    -   2. The milled glass fibres were cleaned using boiling water,        with a strong detergent and with powerful agitation. The        detergent was then rinsed from the fibres.    -   3. 1% w/w of methacryloyloxypropyltrimethoxysilane (Dow Z-6030)        was suspended in water at pH 4 and the fibres added to the        suspension. The resulting mixture was stirred vigorously at room        temperature for 60 minutes.    -   4. The liquid was then drained from the glass fibres, leaving        them still wet with the mixture.    -   5. The Z-6030-treated fibres were then redispersed in water at a        pH of 7.    -   6. Separately, a solution of Z-6030 was reacted with        trimetholylpropane (TMP) in the presence of a tin catalyst (eg        tributyl tin) for 15-20 minutes at 110-120° C. to form a        Z-6030-TMP adduct having a viscosity of about 1200-1500 cP.        Methanol is evolved during the reaction.    -   7. The Z-6030 treated fibres were then reacted with the        Z-6030-TMP adduct to provide a hydrophilic treated fibre. This        was achieved by dispersing the Z-6030 treated fibres in water        and adding the Z-6030-TMP adduct to the water at a concentration        of about 2-3 wt % of fibres. The mixture was stirred together        for approximately 10 minutes. The fibres were then separated and        then centrifuged to remove excess water. The “wet” fibres were        then dried, initially at 30° C. for 3-4 hours, and then heated        to between 110 and 125° C. for 5-7 minutes.    -   8. Separately, an emulsion of polymer was prepared having 200        parts polymers, 100 parts acetone and 16.6 parts water.        Preferably the polymer is a hydrophilic resin such as an        unsaturated polyester.    -   9. The hydrophilic treated fibres were then compounded with the        emulsified resin until evenly distributed in the rations of        about 93 w/w % fibres and 7 w/w % emulsion.    -   10. The compounded fibre-emulsion mixture was then added to the        base resin at approximately 10-45% fibre-emulsion to 90-55%        resin.

Table 1 provides flexural strength data for cured clear casts of thecommercially available Derakane epoxy vinyl ester resin 411-350 (AshlandChemicals). These test panels were prepared according to themanufacturers specifications and the resulted in flexural modulusaverages about 3.1 GPa, the flexural stress at yield averages about 120MPa, and the elongation at break averages between about 5 to 6%.

Table 2 shows similar test panels to those of Table 1 but having beenthermally aged. Panels are thermally aged by heat treatment at 108° C.for two hours follows by controlled cooling to below 40° C. over about 2hours. As can be seen, within experimental error, the flexural modulusand flexural stress are about the same post aging. However, theelongation at break has approximately halved, meaning that the panelshave substantially embrittled with accelerated aging.

TABLE 1 Flexural strength data for cured (un-aged) clear casts ofDerakane 411-350 Epoxy Vinyl Ester Resin. Flexural Modulus FlexuralStress at Elongation at Composite (GPa) Yield (MPa) Break (%) Test Panel1 2.98 112 4.9 Test Panel 2 3.12 119 5.7 Test Panel 3 3.11 123 5.6 TestPanel 4 3.28 132 6.0

TABLE 2 Flexural strength data for aged clear casts of Derakane 411-350Epoxy Vinyl Ester Resin. Flexural Modulus Flexural Stress at Elongationat Composite (GPa) Yield (MPa) Break (%) Test Panel 5 3.30 117 3.0 TestPanel 6 3.40 121 3.1 Test Panel 7 3.10 131 4.1 Test Panel 8 3.20 123 3.6Test Panel 9 3.20 127 4.2

Table 3 provides flexural strength data for aged cured clear casts ofDerakane epoxy vinyl ester resin with various polymer additions(discussed below). As can be seen, the resulting flexural modulusaverages about 3.3 GPa, the flexural stress at yield averages about 135MPa, and the elongation at break averages between about 5 to 7%.Comparing the elongation data between Tables 2 and 3 it can be seen thatthe various polymer additions have substantially reduced agedembrittlement.

TABLE 3 Flexural strength data for aged clear casts of Derakane 411-350Epoxy Vinyl Ester Resin having 12-15 wt % of a polymer additive.Flexural Flexural Stress at Elongation at Composite Modulus (GPa) Yield(MPa) Break (%) Test Panel 10 + polymer 1 3.20 132 6.7 Test Panel 11 +polymer 2 3.20 131 4.9 Test Panel 12 + polymer 3 3.30 136 5.7 Test Panel13 + polymer 4 3.50 140 6.0 Test Panel 14 + polymer 5 3.60 146 6.6

The polymers provided in the tables are the condensation products of apolyol and a diacid. The polyol's and diacid's comprising each polymerare provided in Table 4. These polyesters are generally prepared byheating approximately equimolar amounts of diol and acid at temperaturesin excess of about 200° C. for periods of about 4 to about 12 hours.Most of the unsaturation is present as fumarate diester groups. Thesepolyesters have acid numbers in the range of from about 15 to about 25.(The acid number is the milligrams of potassium hydroxide needed toneutralize one gram of sample).

A 3-liter, round-bottomed flask equipped with a paddle stirrer,thermometer, an inert gas inlet and outlet and an electric heatingmantle. The esterification reactions were conducted in 2 stages. Thefirst stage was reacting the saturated acids in excess glycol, and thesecond stage was carried out with the addition of the unsaturated acidsand remaining glycols. The reactor vessel was weighed between the stagesand glycols were added if needed to compensate for any losses. Themixture was heated to between 150 and 170° C. such that water wasliberated and the condenser inlet temperature was greater than 95° C.

During the next 2-3 hours the temperature of the mixture was raised to240° C. The mixture was then cooled to 105° C. and blended withinhibited styrene. The final polyester resin contained 80 percent byweight of the unsaturated polyester and 20 percent styrene.

TABLE 4 Polyesters used to modify the Derakane base resin in Tables 3and 5. ratio of saturated to Polymer polyol diacid unsaturated acidsPolymer 1 propylene glycol 4 terephthalic acid 2 3:2 moles, MP-diol 1.5moles, isophthalic moles acid 1 mole, fumaric acid 2 moles Polymer 2diethylene glycol 5.5 terephthalic acid 3 3:2. Also, a 0.5M excess molesmoles, fumaric acid 2 glycol was maintained at moles the commencement ofthe second stage Polymer 3 diethylene glycol 6 1,4-cyclohexane 4:3moles, MP-diol 1.5 diacid, fumaric acid moles Polymers 4 Nuplex316/Terephth and 7 50/50 blend Polymer 5 neopentyl glycol 6.251,4-cyclohexane 3:2 moles, propylene diacid 4.5 moles, glycol 2 molesfumaric acid 3 moles Polymer 6 diethylene glycol 1,4-cyclohexane 3:2diacid 3 moles, fumaric acid 2 moles Polymer 8 neopentyl glycol 6.251,4-cyclohexane 4:3 moles, propylene diacid 4 moles, glycol 1 molefumaric acid 3 moles

Table 5 provides flexural strength data for Derakane epoxy vinyl esterresin having the stated ratios of resin to glass fibre (in brackets)wherein the glass fibre is treated only with the Z-6030 coupling agent.

TABLE 5 Flexural strength data for aged Z-6030 treated glass fibres inDerakane 411-350 epoxy vinyl ester resin. Flexural Flexural StressElongation at Composite Modulus (GPa) at Yield (MPa) Break (%) TestPanel 15 (2.3:1) 6.20 124 0.87 Test Panel 16 (2:1) 6.70 129 0.70 TestPanel 17 (1.9:1) 7.50 135 0.63 Test Panel 18 (1.7:1) 8.10 142 0.60 TestPanel 19 (1.6:1) 9.00 149 0.58

Table 6 shows flexural strength data for aged test panels of Derakaneepoxy vinyl ester resin having about 12-15 weight % of a polymeradditive as described above and 45-50 weight % of a treated glass fibreaccording to the present invention.

TABLE 6 Flexural strength data for aged Derakane 411-350 epoxy vinylester resin having 12-15 wt % of a polymer additive and 47 wt % oftreated glass fibre Elongation Flexural Flexural Stress at CompositeModulus (GPa) at Yield (MPa) Break (%) Test Panel 20 + polymer 5 6.10136 2.6 Test Panel 21 + polymer 6 6.20 133 2.2 Test Panel 22 + polymer 65.90 129 2.9 Test Panel 23 + polymer 7 6.00 134 3.1 Test Panel 24 +polymer 8 6.20 135 3.4according to the present invention, wherein the treatment comprises thehydrophilic surface coating and the emulsified polymer.

In the comparison of the flexural data provided in Table 5 and Table 6,it can be seen that the test panels 20-24 according to the presentinvention have significantly improved the elongation at break for agedpanels, providing a reduction in aged embrittlement.

Table 7 provides flexural strength data for aged test panels of Derakaneepoxy vinyl ester resin having the stated ratios of resin to glass fibre(in brackets) wherein the glass fibre is treated with a monomerdeficient resin. Test panel 25 is uncoated and panels 26 to 28 arecoated. Panels having the coated glass fibre show significantly improvedtoughness.

TABLE 7 Flexural strength data for aged test panels of Derakane 411-350epoxy vinyl ester resin having a polymer treated glass wherein thepolymer is a monomer deficient resin. Flexural Flexural StressElongation at Composite Modulus (GPa) at Yield (MPa) Break (%) TestPanel 25 (2.3:1) 6.20 124 0.87 Test Panel 26 (5:1) 3.80 120 4.0 TestPanel 27 (5:1) 3.50 115 4.0 Test Panel 28 (5:1) 3.60 118 4.0

INDUSTRIAL APPLICABILITY

The present invention is useful in a wide variety of industries,including: construction, automotive, aerospace, marine and for corrosionresistant products. The reinforced composite material of the inventionprovides improved long-term mechanical properties compared totraditional glass fibre reinforced materials.

Although the invention has been described with reference to specificexamples, it will be appreciated by those skilled in the art that theinvention may be embodied in many other forms.

The invention claimed is:
 1. A method for producing a reinforcedcomposite material, comprising: coating a plurality of reinforcingfibres with a coupling agent, combining at least one curable resin withsaid coated reinforcing fibres; and curing said at least one curableresin, the cured resin adjacent said reinforcing fibres defining aninterphase, wherein said coated reinforcing fibres are treated such thatthe properties of said interphase are substantially equivalent to thoseof the bulk cured resin, wherein said treatment is a polymeric coatingand a hydrophilic surface coating applied to said coated reinforcingfibres, wherein the polymer of said polymeric coating is a monomerdeficient low activity unsaturated polyester resin and said hydrophilicsurface coating is prepared by reacting a vinyl functional silane with apolyol.
 2. A method according to claim 1 wherein said fibres areunsized.
 3. A method according to claim 1 wherein said coupling agent isa vinyl functional silane.
 4. A method according to claim 1 wherein saidvinyl functional silane is selected from the group consisting of DowCorning Z-6030 (methacryloxypropyltrimethoxysilane), Z-6032(vinylbenzylaminoethylaminopropyltrimethoxysilane), and Z-6075(vinyl-tris(acetoxy) silane).
 5. A method according to claim 1 whereinsaid polyol is trimetholylpropane.
 6. A method according to claim 1wherein said reinforcing fibre is glass fibre.
 7. A method according toclaim 6 wherein the length of said glass fibre is between about 100 and1000 microns.
 8. A method according to claim 1 wherein said propertiescomprise mechanical properties selected from the group consisting ofstrength, toughness, and brittleness or a combination thereof.
 9. Amethod according to claim 1 wherein said properties comprise physical orchemical properties selected from the group consisting of density,cross-link density, chemical resistance, molecular weight and degree ofcrystallinity or a combination thereof.
 10. A method according to claim1 wherein said hydrophilic surface coating further includes treatmentwith an emulsion.
 11. A method according to claim 10 wherein saidemulsion comprises about 16.6 parts water, 100 parts acetone and 200parts polymer.
 12. A method according to claim 10 wherein said emulsioncomprises at least one free radical inhibitor.
 13. A method according toclaim 12 wherein said free radical inhibitor is hydroquinone, a hinderedamine, acetyl acetone, hindered phenols, or combinations thereof.
 14. Amethod according to claim 10 wherein the same polymer is chosen to: a.modify the at least one curable resin to produce a polymer-modifiedresin; and/or b. coat the reinforcing fibres; and/or c. used in thepreparation of the emulsion.
 15. A method according to claim 1 includingthe step of combining a polymer with said at least one curable resin toproduce a polymer-modified resin.
 16. A method according to claim 15wherein said polymer is combined with said at least one curable resin atbetween about 5 to 50% w/w.
 17. A method according to claim 15 whereinsaid curable resin is modified with said polymer to have predeterminedproperties chosen from one or more of tear resistance, strength,toughness and resistance to embrittlement, wherein said properties arerelatively improved when compared to an unmodified curable resin.
 18. Amethod according to claim 15 wherein the cured resin has flexuraltoughness greater than about 3 Joules when tested in a standard flexuretest, the test piece having dimensions about 100 mm in length, 15 mm inwidth and 5 mm in thickness.
 19. A method according to claim 15 whereinthe cured composite material has flexural toughness greater than 3Joules for up to 5 years.
 20. A method according to claim 15 whereinsaid polymer of said polymeric coating or said polymer used to modifysaid curable resin is a monomer deficient low activity unsaturatedpolyester resin.
 21. A method according to claim 15 wherein said monomercontent of said polymer is between about 5 to 30% w/w.
 22. A methodaccording to claim 1 wherein said unsaturated polyester resin isprovided by reacting a polyol with an acid, said polyol being chosenfrom the groups consisting of propylene glycol, methyl propanediol,neopentyl glycol and diethyleneglycol, and wherein said acid is chosenfrom the group consisting of terephthalic acid, isophthalic acid,fumaric acid, and 1,4-cyclohexane diacid, said unsaturated polyesterresin comprising a saturated to unsaturated acid ratio of between about1.2:1 to 2:1.
 23. A method according to claim 1 wherein the flexuralmodulus of the cured composite material is greater than about 3.5 GPa.24. A method according to claim 1 wherein the flexural stress of thecured composite material is greater than about 120 MPa.
 25. A methodaccording to claim 1 wherein the elongation at break of the curedcomposite material is greater than about 2%.
 26. A method according toclaim 1 wherein said fibre is sufficiently coupled to said resin toreinforce said resin.
 27. A method for treating a reinforcing fibre foruse in a composite material including a curable resin, said methodcomprising the steps of: coating a reinforcing fibre with a couplingagent and applying a treatment of a polymeric coating comprising amonomer deficient low activity unsaturated polyester resin, and ahydrophilic surface coating prepared by reacting a vinyl functionalsilane with a polyol, to said coated reinforcing fibre such that, inuse, the cured resin adjacent said reinforcing fibre defines aninterphase, said interphase having properties substantially equivalentto those of the bulk cured resin.
 28. A method according to claim 27wherein said fibres are unsized.
 29. A method according to claim 27wherein said coupling agent is a vinyl functional silane.
 30. A methodaccording to claim 27 wherein said vinyl functional silane is selectedfrom the group consisting of Dow Corning Z-6030(methacryloxypropyltrimethoxysilane), Z-6032(vinylbenzylaminoethylaminopropyltrimethoxysilane), and Z-6075(vinyl-tris(acetoxy) silane).
 31. A method according to claim 27 whereinsaid polyol is trimetholylpropane.
 32. A method according to claim 27wherein said reinforcing fibre is glass fibre.
 33. A method according toclaim 32 wherein the length of said glass fibre is between about 100 and1000 microns.
 34. A method according to claim 27 wherein said propertiescomprise mechanical properties selected from the group consisting ofstrength, toughness, and brittleness or a combination thereof.
 35. Amethod according to claim 27 wherein said properties comprise physicalor chemical properties selected from the group consisting of density,cross-link density, chemical resistance, molecular weight and degree ofcrystallinity or a combination thereof.
 36. A method according to claim27 wherein said hydrophilic surface coating further includes treatmentwith an emulsion.
 37. A method according to claim 36 wherein saidemulsion comprises about 16.6 parts water, 100 parts acetone and 200parts polymer.
 38. A method according to claim 36 wherein said emulsioncomprises at least one free radical inhibitor.
 39. A method according toclaim 38 wherein said free radical inhibitor is hydroquinone, a hinderedamine, acetyl acetone, hindered phenols, or combinations thereof.
 40. Amethod according to claim 36 wherein the same polymer is chosen to: d.modify the at least one curable resin to produce a polymer-modifiedresin; and/or e. coat the reinforcing fibres; and/or f. used in thepreparation of the emulsion.
 41. A method according to claim 27including the step of combining a polymer with said at least one curableresin to produce a polymer-modified resin.
 42. A method according toclaim 41 wherein said polymer is combined with said at least one curableresin at between about 5 to 50% w/w.
 43. A method according to claim 41wherein said curable resin is modified with said polymer to havepredetermined properties chosen from one or more of tear resistance,strength, toughness and resistance to embrittlement, wherein saidproperties are relatively improved when compared to an unmodifiedcurable resin.
 44. A method according to claim 41 wherein the curedresin has flexural toughness greater than about 3 Joules when tested ina standard flexure test, the test piece having dimensions about 100 mmin length, 40 mm in width and 5 mm in thickness.
 45. A method accordingto claim 41 wherein the cured composite material has flexural toughnessgreater than 3 Joules for up to 5 years.
 46. A method according to claim41 wherein said polymer of said polymeric coating or said polymer usedto modify said curable resin is a monomer deficient low activityunsaturated polyester resin.
 47. A method according to claim 41 whereinsaid monomer content of said polymer is between about 5 to 30% w/w. 48.A method according to claim 27 wherein said unsaturated polyester resinis provided by reacting a polyol with an acid, said polyol being chosenfrom the groups consisting of propylene glycol, methyl propanediol,neopentyl glycol and diethyleneglycol, and wherein said acid is chosenfrom the group consisting of terephthalic acid, isophthalic acid,fumaric acid, and 1,4-cyclohexane diacid, said unsaturated polyesterresin comprising a saturated to unsaturated acid ratio of between about1.2:1 to 2:1.
 49. A method according to claim 27 wherein the flexuralmodulus of the cured composite material is greater than about 3.5 GPa.50. A method according to claim 27 wherein the flexural stress of thecured composite material is greater than about 120 MPa.
 51. A methodaccording to claim 27 wherein the elongation at break of the curedcomposite material is greater than about 2%.
 52. A method according toclaim 27 wherein said fibre is sufficiently coupled to said resin toreinforce said resin.
 53. A method for moulding a composite materialcomprising the steps of providing a mixture of at least one curableresin and a plurality of reinforcing fibres produced by the methodaccording to claim 27, applying the mixture to a mould and curing the atleast one curable resin.